Production of pectin from soybeans

ABSTRACT

A novel process for extracting pectin from waste hull/hypocotyl streams during soybean processing is disclosed. Chemical extracting agents in addition to or in conjunction with heat and agitation are used to extract pectin from the waste streams. The pectin is then precipitated in alcohol, washed and dried. A process for whitening the extracted pectin is also disclosed.

RELATED APPLICATIONS

[0001] This application claims provisional priority to U.S. ProvisionalApplication Serial Nos.: 60/166,773, filed 22 Nov. 1999 and 60/212,153,filed 6 Jun. 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a novel process to extractpectin from a waste hull/hypocotyl stream during soybean processing andto a whitened form of soy pectin.

[0004] More particularly, the present invention relates to a novelprocess to extract pectin from waste soybean hull/hypocotyl streamsusing a chemical extraction agent in addition to heat and agitationfollowed by precipitation in alcohol, drying and whitening and to awhitened soy pectin product.

[0005] 2. Description of the Related Art

[0006] US farmers produce about half of the 140 million metric tons ofsoybeans produced worldwide each year (Klugh 1997, Am. Soybean Assoc.1998). All but 1 million metric tons are oil type beans that are crushedand made into soybean oil for human food products or soybean oil as anindustrial feed stock. The defatted soybean meal is used mainly foranimal feed. Oil soybeans are composed of about 90% cotyledons, 8% hullsand 2% hypocotyls. Soybean hulls and about 40% of the hypocotyls aresold separately for $0.07 to $0.08/kg and are referred to as soy “millrun” for use as animal feed. Mill run is about 95% hulls that arecomposed mostly of alpha cellulose and hemicellulose; they contain about9% protein and are low in lignin. The digestible energy of soy hulls isessentially equal to grains for ruminant animals (Liu 1997). The soyhull pectins of this invention are suitable as a dietary fiber source,i.e., as a dietary supplement or a food additive.

[0007] Dietary fiber plays a strong supporting role in manynutraceutical foods where the fiber works in combination with healthpromoting ingredients such as nutraceuticals and antioxidants (Pszczola1998). Glore, et al. 1994, reviewed the effects of pectin and othersoluble dietary fibers on serum lipids and reported that in 88% of the77 human studies, soluble fiber significantly lowered total serumcholesterol (TC). Of the studies that reported on the effect of aspecific food or type of soluble fiber, beans and legumes reduced TC in100% (10/10) and pectin reduced TC in 71% (10/14) of these studies.Hunninghake et al. 1994 and Kumar et al. 1997 found similar results.Judd and Truswell 1982 compared the effects of high methoxyl pectin witha degree of esterification (DE) of 71%, to low methoxyl pectin, DE 37%,and found both almost equally effective in lowering TC in humans. In1980 Jeltema and Zabik reported on the pectin content of soybean hulls.In the water-soluble fraction they found about 0.5% pectin and 0.4%hemicellulose and in the water-insoluble fraction they found 7% pectin,36% cellulose, 18% hemicellulose and 3% lignin. Gnanasambandam andProctor 1999 reported on the X-ray diffraction and infrared spectra oflaboratory extracted pectins. The specific cholesterol lowering abilityof soybean pectin has yet to be established.

[0008] Soy, together with several other types of fiber, is being used ina wide variety of nutraceutical food products. Nutraceutical drinks andhigh fiber instant noodles use soy fiber to reduce fat and increase thehealth benefits from high dietary fiber levels (Pszczola 1998). Aconsiderable amount of research done on the chemical analysis of peahulls demonstrated that pea hulls alcohol insoluble residue (AIR) was94% carbohydrate including 4 to 6% pectinaceous material (Weightman, etal. 1994). Functional properties of the AIR showed high cation exchangecapacity and significant water holding and swelling capacities. Dalevand Simeonova, 1995 combined positively charged proteins below theirisoelectric point with anionic pectin to produce stable, low oilemulsions for creams and mayonnaises with a high dietary fiber content.Low-methoxyl pectins have been studied as potential moisture barriers inedible coatings (Kester and Fennema 1986) and as low-caloriefat-replacers with improved mouthfeel in salad dressings, frozen desertsand baked goods (Glicksman 1991).

[0009] Most commercial pectin is extracted from citrus peel recoveredafter the juicing operation. Heat and mineral acids are used tosolubilize the pectin and either alcohols or aluminum salts aregenerally used for precipitin. Commercial pectin is also extracted fromapple pomace in a similar manner (May 1990). Both citrus peel and applepomace are high in moisture and are typically dried within a few hoursafter the juicing operation to prevent attack by moulds and nativepectic enzymes. There is an accompanying loss in pectin yield withdrying, 15% to 30% for lemon peel (Crandall, et al 1978). A dry startingmaterial like soy hulls and hypocotyls would be stable for long periodsof time and not have the expense of needing to be dried, a distinctadvantage.

[0010] Thus, there is a need in the art for pectins derived from othersources and especially pectins with improved color using a low valuestarting material such as soybeans and equipment that can beincorporated into existing soybean processing plants.

SUMMARY OF THE INVENTION

[0011] The present invention provides a soybean derived pectin havingenhanced whiteness.

[0012] The present invention also provides a soy pectin materialcomprising about 40 wt. % of anhydrous galacturonic acid and about 8 wt.% protein.

[0013] The present invention also provides a food stuff for animalsincluding humans comprising the soy pectin of this invention.

[0014] The present invention also provides a method for extracting soypectin from soybeans during soybean processing involving acidificationof waste soybean hull/hypocotyl streams at an elevated temperature underagitation followed by alcohol precipitation and drying. Optionally, themethod can include water and additional alcohol washing steps.

[0015] The present invention further provides a method for improving thewhiteness of soy pectin involving slowly evaporating the alcohol fromthe precipitated soy pectin over a period of time sufficient to enhancethe whiteness, preferably the period is at least one hour andparticularly at least 2 hours and especially at least 3 hours.

[0016] The present invention also provides a method for producing soypectin comprising the steps of: extracting a soybean hull/hypocotylmixture in a mineral acid at an elevated temperature and for a time andat a pH sufficient to extract a pectinaceous soy material from themixture; cooling the extracted pectinaceous material and raising the pH;separating the extract from the solid residue; precipitating thepectinaceous material in an alcohol; and drying the pectinaceousmaterial to form soy pectin.

DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 depicts a typical commercial soybean processing plant flowdiagram showing hot de-hulling and separation of hulls and hypocotyls;

[0018]FIG. 2 depicts a small pilot plant flow diagram showing washing,soaking, extraction and precipitation conditions;

[0019]FIG. 3 depicts a cross-section of pilot plant-scale, continuous,solid bowl centrifuge; and

[0020]FIG. 4 depicts a large pilot plant flow diagram giving materialbalance and yields of pectin from commercial soybean hull and hypocotylmixture.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The inventors have found that pectin can be extracted from wastehull/hypocotyl streams from soybean processing. Chemical extractingagents such as minerals acids, alkali bases and enzymes in addition toor in conjunction with to heat and agitation are used to extract pectinfrom soyben hull/hypocotyl waste stream. The extracted pectin can thenbe precipitated in alcohol, dried and evaluated. The process uses a lowvalue starting material to produce pectin. Pectin is a valuablecommodity in the food industry and most pectin is currently importedinto the United States. Also, the process has been developed usingmaterials and equipment that can be incorporated into existing soybeanprocessing plants.

[0022] Soy pectin may be a low cost substitute for citrus and applepectin in the manufacture of jams, jellies, candies, fat replacers andpharmaceuticals. Pectin may also possess phytochemical properties suchas the reduction of hypercholesterolemia (high cholesterol) and pectinhas many uses as a food additive.

[0023] The inventors have found that a soy pectin can be prepared thathas a lightness index above about 85 L, preferably above about 87 L andparticularly above about 90 L. The lightness index is a scaled indexdepicting the darkness or lightness of the product. The index start witha value of zero being black to a value of 100 being white. Furtherdetails about the index can be found in Norman Potter and JosephHotchkiss, 1995, “Food Science” 5^(th) edition, Chapman and HallPublishing, NY, N.Y., pages 93-95, incorporated herein by reference.

[0024] Pre-wash Unit Operation

[0025] Extraction of pectin from samples of soybean hulls and hypocotylswith mineral acids was initially not successful. The dried pectin wascolored dark brown, brittle, very hard and resistant tore-solubilization after being dried under vacuum. It was determined thatusing a pre-wash step before extracting the soy hulls and hypocotyls hada beneficial effect on the purity of the finished product. This pre-washstep removed soluble hemicellulose and other soluble compounds thatinterfered with the extraction of the pectin. Mass balance showed thatabout 15% of the dry weight of the starting materials was removed duringthe wash step.

[0026] During the wash temperature study at 20° C., 50° C., 60° C., 70°C. and 90° C., the yield of pectin decreased significantly as thepre-wash water temperatures were increased above 20° C. as shown inTable 1. TABLE 1 Comparison of Wash Temperatures Using Turbidity of theLeach Water, % Yield of Pectin and % Purity of Pectin % T Wash Second %Yield of % Purity as Temp. First Wash Wash pectin UA 20° C. 8.7 ± 1.136.8 ± 0.9 8.1 ± 0.7 26 ± 4 50° C. 7.2 ± 0.8 31.9 ± 1.1 4.7 ± 0.4 27 ± 460° C. 7.4 ± 0.7 32.6 ± 4.5 5.4 ± 1.1 30 ± 4 70° C. 8.8 ± 1.1 43.6 ± 3.94.6 ± 0.0 38 ± 4 90° C. 7.4 ± 0.8 40.4 ± 4.9 4.6 ± 0.1 42 ± 4

[0027] Two, 10-minute ambient temperature, 20° C., pre-washes were foundto be adequate to remove interfering soluble compounds for an increasein pectin quality and purity without an extensive reduction in the yieldof pectin.

[0028] Soaking Unit Operation

[0029] The purpose of soaking was to expand the cellular network andfacilitate pectin extraction to increase the yield. Soaking the hullsand hypocotyls at room temperature at a pH of 2.0-2.4 for 18 hours wascompared to soaking for 7 days. There was no significant differencebetween soaking for 18 hours yield, 9.8±0.9%, when compared to soakingfor seven days, 9.4±0.5% yield. This indicated that for the proposedpectin extraction conditions, soak times longer than 18 hours did notrelease a greater amount of pectinaceous materials from the cellularmatrix. Longer presoaking times also produced a darker-colored pectin.Data not shown.

[0030] The pH range of 2.0-2.4 was chosen based on information obtainedfrom a 1938 patent by Olsen and Stuewer. This pH loosened the cellularmatrix without damaging the pectinaceous material and minimizedincreases in the microbial load. Soaking of starting materials prior topectin extraction has been used to a limited extent commercially. It wasused to store fresh lime and lemon peel to prevent rapid degradation ofpectin by native endopolygalacturonase enzymes. Soaking at a reduced pHalso helped soften the citrus peel and prevent microbial degradation(Ehrlich, 1998).

[0031] Small Scale Pilot Plant Extractions

[0032] The preliminary laboratory experiments were finalized and scaledup for small-scale extractions in the pilot plant as shown in FIG. 2.The pectinaceous material extracted in the small-scale, pilot plantoperation and separated using press cloths gave a yield of 3.0%. Thecolor of this sample was L*80.7+/−4.1, a*1.2+/−0.5, b*10.7+/−1.6. Whencompared to commercial lime pectin with a color of L*91.6, a*1.8,b*14.6, the soy pectinaceous material was found to be slightly darker incolor. Typically pectin extracted from lime or lemon peel has a yield ofabout 30% and a purity greater than 65% (Crandall, et al. 1978). Theminimum 65% purity as galacturonic acid is required by USP Standards.The inventors were unable to achieve a high methoxyl gel formation withthe soy pectinaceous material using the excess acid in the glass method(IFT 1959) with this particular preferred extract. Thus, the soybeanpectin product is different from traditional citrus pectin and acts moreas a thickener than a gelling agent.

[0033] 50 g from the third small-scale pilot plant extraction wasanalyzed for its chemical constituents and the results are shown inTable 2. TABLE 2 Analysis of Pectic Polysaccharide from Soybeans Purityas AGA* 41.3% Xylose + mannose 16.0% Galactose 7.6% Rhamnose 1.4%Glucose 4.3% Arabinose 2.5% Fucose 1.2% Cellulose 0.6% Protein 7.9% (N *6.25) Moisture 2.3% Total analyzed 85.1%

[0034] These results indicate that the pectinaceous substances isolatedfrom soybean hulls and hypocotyls are a pectin backbone composed ofrharmnogalacturonic and xylogalacturonic acids. They had a galacturonicacid content of 41.3% and a xylose/mannose content of 16%. There weresignificant amounts of galactose and glucose and small amounts ofrhamnose and arabanose. After extensive aqueous washing of the rawmaterial, alcohol washing/precipitation and alcohol washing/pressing ofthe pectinaceous product, the loosely held sugars that were part of thephysical matrix had been removed. Therefore, the remaining sugars musthave been part of the pectinaceous molecules. These results are similarto the commercial SPS soy product reported on by Beldman et al. 1996with a similar galacturonic acid and neutral sugars content forgalactose and arabinose from a soluble ‘hairy’ pectic polysaccharide ofsoy (Adler-Nissen et al. 1984).

[0035] The soy pectinaceous material extracted under the conditionsdescribed in FIG. 2 had a degree of esterification (DE) of 29.6% with amethoxyl content of 1.67% indicating a low methoxyl (LM) pectin.Weightman, et al 1994 and 1995, found the alcohol insoluble residue(AIR) from another legume, pea hulls, also had a low degree ofmethylation.

[0036] There was a fairly high degree of acetylation, 27.2%, of the acidextracted soy pectinaceous material. The total acetyl content of 2.1%.The average molecular weight of the soy pectinaceous material wasapproximately 21 kD. Only 85% of this soy pectinaceous sample wassoluble including about 8% that was protein. The remaining insolubleportion was assumed mostly to be insoluble cellulose and hemicellulose.

[0037] Large Scale Pilot Plant Extractions

[0038] The goal of the large-scale tests was to produce several hundredgrams of pectinaceous material from soy mill run for commercialevaluations. This amount of product required three or four large-scalepilot plant runs and a centrifuge for the separation of the spent hullsfrom the pectin liquor. The solid bowl centrifuge was able to separatethe extracted pectin suspension with feed solids of about 40% solids andreduce it to less than 6% solids in the centrifuged pectin liquor. FIG.4 shows the overall process and material balance values from one of thelarge scale, pilot plant runs. From 9 kg of the commercial soy hull andhypocotyl mixture, the process of this invention extracted approximately500 g of pectin with a yield of 5.6% and an UA of 37%.

[0039] Limited application studies of the soy pectinaceous material atDanisco-Cultor showed it had thickening capabilities in a milk-baseddrink. One negative aspect for the milk-based drink was a proteinprecipitating capacity. The inventors anticipate that the soypectinaceous material of this invention will be a suitable for many usesin the food industry.

[0040] Traditionally, soy hulls and hypocotyls are fed to ruminants asan energy source when the ruminants are on a cool season forage. Thefeed analysis on a composite sample from the large scale run before andafter acid extraction showed there were no major differences in thedigestibility of the feed before and after acid extraction of thepectin. Therefore, it was important in completing this feasibility studyof the pectin extraction process to measure the differences in thefeeding value before and after extraction. Results from the feedanalysis estimated the energy content in the soy hulls before and afterextraction as shown in Table 3. TABLE 3 Feed Analysis of CompositeSample of Soy Hull and Hypocotyl Before and After Acid Extraction ofPectin Dry Matter Basis In Vitro (Tannin) % % Neutral % Acid % AcidDigestibility [Catechin % % Dry % Crude Detergent Detergent Detergent %Hemi- % % equivalent/ Moisture Matter Ash Protein Fiber Fiber LigninCellulose Cellulose IVDMD g sample] Before NA 93.00 4.99 13.67 77.1251.07 2.16 26.05 48.75 84.04 0.02 Extraction After 72.46 92.20 3.2012.91 68.01 66.54 2.78 1.47 63.57 78.14 0.04 Extraction Dry Matter BasisNa S K Mn Fe Cu Zn Al Ca Mg P (mg/kg) (%) (%) (mg/kg) (mg/kg) (mg/kg)(mg/kg) (mg/kg) (%) (G) (%) Before 622.63 0.07 1.42 48.56 870.53 9.4867.67 567.42 0.61 0.26 0.14 Extraction After 3488.08 0.06 0.16 30.25434.45 7.76 48.58 142.71 0.62 0.13 0.08 Extraction

[0041] The crude protein dropped less than 1% but is still adequate atalmost 13%. The NDF and hemicellulose reflect the acid extractionconditions that led to a higher percentage of cellulose in the extractedsample. Both the lignin (ADL) and tannin were low in these samples. Thedigestibility, % IVDMD, is excellent at about 80% compared to alfalfa at70 to 72%. Typical coefficients of variation are less than 2% usingthese feed analysis techniques. The soy hulls and hypocotyls afterextraction are still a good source of energy for ruminants. The moisturein the extracted mill run, about 70%, is similar to green corn and haspotential for use in silage. The hot, nitric acid extraction removedabout 1.8% of the ash and can be seen as a general decrease in most ofthe minerals. Thus, soy hull and hypocotyl, that have had the pectinextracted, will still be useful as a feed that is used principally as anenergy source despite a decrease in mineral content.

[0042] The pectinaceous material extracted from soybean hulls andhypocotyls is useful in all applications where other pectins are useful.The use of soluble fiber and mixtures of soluble and insoluble fiber infood products is growing rapidly (Andersson 1994, Garcia, et al. 1991,Thestrup 1993, Yamaguchi, et al. 1994). The inventors have proved thatthe major portion of pectinaceous materials from the soy hulls isextractable and a viable commerce product is formed. Quantitativeextraction of dietary fiber components from soy has already beenpublished (Jeltema and Zabik 1980).

[0043] The fact that the soy pectinaceous material is different fromcitrus pectin has several advantages. The citrus industry has along-standing market share using pectin as a food ingredient and a new,similar product would have difficulty competing. One of the limitationsof citrus pectin as a nutraceutical is the formation of strong gels atlow concentrations (Yamaguchi, et al. 1994). Lower molecular weight andlow methoxyl pectins are being prepared from high molecular weight andhigh methoxyl pectins for nutraceutical and functional purposes(Yamaguchi, et al. 1994, Thestrup 1993). The soy pectinaceous materialis extracted with a low molecular weight and a low methoxyl content andmay be more economically feasible as a functional and/or nutraceuticalfood additive. If the soy pectinaceous material is found to have healthbenefits, such as a cholesterol lowering ability, it can be added tofoods in relatively large quantities without changing the texturalproperties of the foods too greatly. With 70 million metric tons ofsoybeans produced in the US each year and 8% of this amount is low-valuemill run containing 6% pectinaceous material, there is a potentialproduction of more than 100 thousand tons annually. The inventors haveshown that soy mil run can still by used as a cattle feed after pectinextraction and could increase the profits to soybean growers andprocessors.

EXAMPLES

[0044] Materials

[0045] Commercial samples of a soybean hull and hypocotyl mixture wereobtained from a soybean processing line of a major soybean processor inStuttgart, A R. All chemicals (nitric acid, sodium hydroxide,2-propanol, m-phenylphenol) were purchased from Fisher Scientific,Pittsburgh, Pa.).

[0046] Methods

[0047] Phase 1: Laboratory-Scale Experiments

[0048] Soy hulls and hypocotyls were collected from a commercial soybeanprocessing plant after hot de-hulling and an initial separation of thehulls from the broken pieces of cotyledon. The starting materials forthis experiment, a commercially available hull and hypocotyl mixture,was mixed and randomly assigned to sub-samples. A series of preliminaryexperiments were designed to adapt citrus pectin preparation andextraction procedures to the extraction of pectinaceous materials fromsoybean hulls and hypocotyls. All experiments were done in duplicate.

[0049] Samples of soy hulls and hypocotyls were washed to determine theeffects of wash water temperatures. The percent transmittance (%T) wasmeasured on the wash solutions with a Coleman-Hatachi model 101spectrophotometer (Maywood, Ill.). Separate experiments were conductedto increase the yield of pectin by soaking the washed hulls andhypocotyls to expand their cellular matrix. An 18-hour soak at ambienttemperature was compared with a 7-day soak at pH 2.0-2.4 adjusted withnitric acid, an acid commonly used in commercial pectin extractionoperations.

[0050] The following extraction conditions were optimized in thelaboratory. 60 g of hulls and hypocotyls was washed twice with ambienttemperature water with rapid stirring for 10 minutes. The dirty washwater was filtered from the hulls and hypocotyls. They were then soaked18 hours in 1 L of ambient temperature water adjusted to pH 2.0-2.4using nitric acid. After the wash and soak steps, the hull and hypocotylmixture was extracted at 90° C. and pH 1.8 for 45 min with rapidstirring. After heating, the pH was readjusted to approximately pH 4.0using sodium bicarbonate to minimize damage to the pectinaceous product.The pectin liquor was separated from the spent hulls by filtration andprecipitated for 18 hours in 2× volumes of 100% 2-propanol before beingfiltered from solution. The pectinaceous material was rinsed twice in70% 2-propanol and once in 100% 2-propanol before drying overnight atroom temperature to evaporate the alcohol and under vacuum at 55° C. for18 hours to evaporate the water. These preliminary lab-scale experimentsset the conditions for the larger-scale pilot plant extractions.

[0051] The pectinaceous material from each of the extractions wascharacterized for % yield, color and purity. The color of the dried,ground pectin was measured on a Gardner/Pacific Scientific colorimeter(Model 05, Silver Springs, Mass.). The galacturonic acid (UA) contentwas measured by the m-hydroxydiphenyl method as modified by Kintner andVanBuren 1982 using a Coleman-Hitachi model 101 spectrophotometer.

[0052] Referring now to FIG. 1, an block diagram 100 for a preferredembodiment of a process of this invention is shown to includes aconditioning step 102 where the water content of a soybeans is reducedor increased to about 13 to about 16 percent. Higher and lower waterpercentages can be used as well. Next, the conditioned soybeans arecleaned using air and screen to remove foreign material in a cleaningstep 104. After cleaning, the soybeans are dried to about 10.5% moisturecontent in a drying step 106. Next, the soybeans are heated to about 70°C. with heated air and/or steam in a heating step 108. After heating,the soybeans are mechanically cracked between two rollers into about 8pieces in a cracking step 110. Next, the hulls and hypocotyls areremoved from the pieces with rubber rolls or other mechanical means inremoving step 112. After removal, the hulls and hypocotyls are separatedfrom the bean pieces in a counter-current air stream in separating step114. After separation, the hulls and hypocotyls, small pieces ofcotyledons and hypocotyls are separated from the hulls in a separatingstep 116. Recovered small pieces of cotyledons and hypocotyls are flakedin a flaking step 118. Recovered hulls and remaining hypocotyls areground in a grinding step 120. Finally, the ground hulls and hypocotylsor mill run solids have been processed into animal feed in a packagingstep 122.

[0053] Phase 2: Small Pilot Plant Extractions

[0054] The lab procedures were then scaled-up in a series of three smallpilot plant-scale runs using 1.8 kg of the commercial hull and hypocotylmixture each time. This is an intermediate step in the scale-up processand was 30 times larger than the laboratory scale. The starting materialwas washed twice with 30 L ambient temperature water. After each washingthe solids were separated from the dirty wash water using a Langenkampfinisher, model 185SG. The material was then soaked for 18 hours in 30 Lof ambient temperature water after adjusting the pH to 2.4 with nitricacid. The pectinaceous materials were extracted in a steam-jacketedkettle with rapid stirring at 90° C. and pH 1.8 for 45 minutes. Thepectin liquor was separated from the spent hulls using mechanicalpressing through press cloths. After mechanical pressing, the pectinliquor can be ultra filtered to a liquid concentration of 0.5 to 3-5%.After precipitation in 2×volumes of 100% 2-propanol, three rinses in 70%and 100% 2-propanol and drying, approximately 50 g of the pectinaceousmaterial from the third run was analyzed by Danisco-Cultor, Brabrand,Denmark for chemical composition.

[0055] Referring now to FIG. 2, an block diagram 200 for anotherpreferred embodiment of a process of this invention is shown to includesa start step 202 where a 1800 gram soy hull and hypocotyl sample startsits way through the purification and whitening process of thisinvention. The hull and hypocotyl sample is washed until %T (turbidity)is less than about 35% in a washing step 204. After washing, the sampleis soaked in room temperature water adjusted to a pH of about 2.4 in asoaking step 206. Next, the sample is extracted at a pH of about 1.8 forabout 45 minutes with agitation at a temperature of about 90° C. in anextracting step 208. After extracting, the extracted sample is cooled toabout 55° C. and the pH is adjusted to about 4.2 with sodium carbonatein a cooling step 210. Next, a liquid component of the cooled sample isseparated using mechanical press cloth in a separating step 212. Itshould be recognized that any liquid separating apparatus can be usedprovided the apparatus does not result in the decomposition of thepectinaceous material. After separation, the liquid can be concentratedin an ultra filtration step 214; although, preferred, the step can beomitted. After ultra filtration, the liquid is precipitated in 2 volumesof 2-propanol in a precipitating step 216. After precipitation, thesolids are washed three times with 70% propanol and 2 times with 100%2-propanol with mechanical pressing between each wash in a washing step218. Although 2-propanol is preferred other alcohols can be usedpreferably primary and secondary alcohols having between about 2 andabout 10 carbon atoms. After washing, remaining alcohol is allowed toevaporated over a period of time and then the solids are dried in vacuumat about 50° C. for about 18 hours in an evaporating/drying step 220.Next, the dried solids are ground to pass through a 20 mesh screen in agrinding step 222. After grinding, the solids are stored under dryconditions for evaluation in a storing step 224. Of course, that thispoint, the solid can be used to prepare any food stuff that uses pectin.Thus, the present invention also relates to any food stuff containingthe soy pectin of this invention.

[0056] Phase 3: Large Scale Pilot Plant Tests

[0057] Based on the small scale extractions, a series of fourlarge-scale pilot plant extractions was performed on 9 kg of the hulland hypocotyl mixture that was washed, soaked and extracted in 80 L ofwater at 90° C. and pH 1.8 for 45 min. An overhead mixer, Lightning(Avon, N.Y.), was used to provide continuous agitation during theextraction to aid in acid penetration and removal of pectin from thehulls. An extraction of this size prohibited the use of batchfiltration, so preliminary tests were run to determine the operatingparameters for a pilot plant-scale, continuous, solid bowl centrifuge(Derrick Corporation, Buffalo, N.Y. 14225). The pilot-plant scalecentrifuge was loaned to us by Derrick Corporation whose employeesworked with us to refine the separation techniques and the centrifugeoperating conditions.

[0058] This solid bowl centrifuge has one drive mechanism for the bowland a separate drive mechanism that turns a conveyer to remove thesolids from inside the bowl as shown in FIG. 3. Looking at FIG. 3, apreferred centrifuge unit 300 for use in the practice of this inventionis shown to include a slurry inlet 302, a housing 304, a screw 306, aplurality of flights 308, a solid discharge 310 and a liquids discharge312. The screw 306 is shown to turn in a direction shown in arrow 314.

[0059] The solid bowl centrifuge speed of 5,000 rpm (3750 RCF) was foundto be sufficient to remove most of the fine materials remaining afterthe extraction. The conveyer was run at 3,100 rpm in the directionopposite to the bowl to give a net speed of 20 rpm conveying the solidsout of the bowl. The tapered, conical end of the centrifuge acts like aninclined plane where the solids are drained as they are conveyed up andout of the centrifuge. The solids content of the feed and stream thathad been centrifuged was determined using a Beckman model TJ-6centrifuge (Fullerton, Calif. 92835).

[0060] The pectinaceous material was precipitated in 2×volumes of 100%2-propanol overnight and washed with 70% and 100% 2-propanol (FIG. 4).The removal of the alcohol solution and rinse solutions was accomplishedwith press clothes. Approximately 800 g of this product was analyzed forfunctionality and applications.

[0061] In this feasibility study, the inventors also explored howeconomically the soy hulls and hypocotyls remains could be disposedafter extracting the pectin. Composite samples of the soy hulls andhypocotyls were analyzed to determine if the extracted soy hulls couldstill be used as an energy source for ruminants. Samples were dried at55° C. in a forced air oven for 18 hours to determine the moisturecontent prior to grinding. A representative sample was dried at 100° C.in a convection oven for 18 hours to determine the dry matter content.All of the analysis are reported on a dry matter, bone-dry-basis.Composite samples of the starting materials and extracted soy hulls andhypocotyls were analyzed for neutral detergent fiber (NDF), aciddetergent fiber (ADF) and acid detergent lignin (ADL) using amodification of the Van Soest procedure (Goering and Van Soest 1970)with the filter bag technique (Ankom²⁰⁰ Fiber Analyser: Ankom TechnologyCorporation, Fairport, N.Y.). Samples were also analyzed for in vitrodigestibility IVDMD by the method of Tilley and Terry 1963. Dry matter,ash and crude protein as Kjeldahl nitrogen were run by the AOAC 1984method and tannin content was analyzed by the procedure of Burns 1971 asmodified by Price et al. 1978. Mineral analysis was performed byinductively coupled plasma (Spectro Analytical Instruments, SpectroFlame Module E).

[0062] Referring now to FIG. 4, an block diagram 400 for anotherpreferred embodiment of a process of this invention is shown to includesa start step 402 where a 9 kilogram soy hull and hypocotyl sample startsits way through the purification and whitening process of thisinvention. The hull and hypocotyl sample is washed and drained 4 timesin 200 L of water in a washing step 404. Of course, additional washedcan be used as well. Moreover, less washes can be used, but theresulting process is less preferred. After washing, the sample is soakedin room temperature water adjusted to a pH of about 2.4 in a soakingstep 406. Next, the sample is extracted at a pH of about 1.8 for about45 minutes with agitation at a temperature of about 90° C. in anextracting step 408. After extracting, the extracted sample is cooled toabout 70° C. and the pH is adjusted to about 4.2 in a cooling step 410.Next, a liquid component of the cooled sample is separated using acentrifuge @3750 RCS at a flow rate of about 9.5 L/min in a separatingstep 412. It should be recognized that any liquid separating apparatuscan be used. provided the apparatus does not result in the decompositionof the pectinaceous material. After separation, yielded about 82 L of acrude pectin liquor and about 22 kgs of extracted solids in recoveringstep 414; although, preferred, the step can be omitted. Next, the liquidis precipitated into 2-propanol with agitation and held in theprecipitating environment for about 18 hours in a precipitating step416. After precipitation, the solids are washed three times with 70%propanol and 2 times with 100% 2-propanol with mechanical pressingbetween each wash in a washing step 418. Although 2-propanol ispreferred other alcohols can be used preferably primary and secondaryalcohols having between about 2 and about 10 carbon atoms. Afterwashing, remaining alcohol is allowed to evaporated over a period ofabout 48 hours ate room or ambient temperature and then dried undervacuum at about 50° C. for about 18 hours in an evaporating/drying step420. This process afforded 511 grams of a pectaneous material, a yieldof about 5.6% in a recovering step 422. Of course, that this point, thesolid can be used to prepare any food stuff that uses pectin. Thus, thepresent invention also relates to any food stuff containing the soypectin of this invention.

[0063] Although several preferred processes of this invention aredescribed above, it should be recognized that the times and temperaturesset forth in these embodiments are preferred times and temperatures andshorter and longer times are permitted as well as high and lowertemperatures are permitted.

REFERENCES

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[0094] All references cited herein are incorporated by reference. Whilethis invention has been described fully and completely, it should beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. Although theinvention has been disclosed with reference to its preferredembodiments, from reading this description those of skill in the art mayappreciate changes and modification that may be made which do not departfrom the scope and spirit of the invention as described above andclaimed hereafter.

We claim:
 1. A pectin comprising soy pectinaceous material having alightness index above about 85 L.
 2. The pectin of claim 1, wherein thelightness index is above about 87 L.
 3. The pectin of claim 1, whereinthe lightness index is above about 90 L.
 4. The pectin of claim 1,wherein the pectin comprises about 40 wt. % galacturonic acid, about 16wt. % of a mixture of xylose and mannose, about 8 wt. % galactose, about1.5 wt. % rhamnose, about 4 wt. % glucose, about 2.5 wt. % arabinose,about 1.5 wt.% fucose, acout 1 wt. % Cellulose, about 8 wt. % proteinand about 2% moisture.
 5. The pectin of claim 1, wherein the pectin hasabout 40% by weight galacturonic acid and about 16% by weight of amixture of xylose and mannose.
 6. The pectin of claim 1, wherein thepectin has about 25% by weight of esterified sugar residues and amethoxyl content of about 1.5%.
 7. The pectin of claim 1, wherein thepectin has a degree of acetylation of about 25%.
 8. The pectin of claim1, wherein the pectin has a molecular weight of about 21 kD.
 9. Thepectin of claim 1, wherein the pectin has an AGA purity of about 55%.10. The pectin of claim 1, wherein the pectin has an AGA purity above60%.
 11. A method for producing soy pectin comprising the steps of:extracting a soybean hull/hypocotyl mixture in a mineral acid at anelevated temperature and for a time and at a pH sufficient to extract apectinaceous soy material from the mixture; cooling the extractedpectinaceous material and raising the pH; separating the extract fromthe solid residue; precipitating the pectinaceous material in analcohol; and drying the pectinaceous material to form soy pectin. 12.The method of claim 11, further comprising the step of: pre-washing thehull/hypocotyl mixture in the presence of a solvent for a time andtemperature sufficient to produces a pre-extraction mixture has apercent transmittance above about 35% on liquid.
 13. The method of claim12, further comprising the step of: soaking the washed hull/hypocotylmixture in the presence of a solvent for a time, temperature and pHsufficient to expand the cellular matrix of the washed mixture.
 14. Themethod of claim 11, further comprising the step of: post-washing theprecipitated pectinaceous material with pressing in the presence of asolvent sufficient number of times to wash the material.
 15. The methodof claim 14, wherein the post-washing step comprising: three 70%2-propanol washings and two 100% 2-propanol washings with pressing aftereach washing.
 16. The method of claim 14, further comprising the stepof: slowly evaporating the 2-propanol from the pectinaceous material fora time sufficient to enhance the whiteness of the pectin product. 17.The method of claim 11, further comprising the step of: evaporating thepectinaceous material under a vacuum at an elevated evaporationtemperature.
 18. The method of claim 11, further comprising the step of:grinding the pectin product.
 19. A food stuff comprising a soypectinaceous material having a lightness index above about 85 L.
 20. Afood additive comprising a soy pectinaceous material having a lightnessindex above about 85 L.